1. Field of the Invention
The present invention relates generally to the field of material handling equipment, and more particularly but not by way of limitation, to an improved method and apparatus for prefeeding stacked paperboard products at high speeds wherein such products are shingled prior to further processing.
2. Discussion
The packaging of products in paperboard containers or boxes has increased so much over the years that a very large packaging industry has emerged. It is common to cut paperboard container blanks from planar sheets of corrugated composition. The blanks are then removed of excess trim and stacked flat in bundles for movement to points of usage.
The work function which is addressed by the present invention is that of prefeeding the flats or blanks in stacks of sheets, shingling the sheets and passing same to other processes within a paperboard products plant. Further, it is often desired that the bottom most sheet of a stack of sheets be removed because this bottom most sheet really serves as a dunnage sheet, becoming marred by the travel of the stack on roller conveyors that move such stacks in a paperboard products plant. This is exacerbated by the fact that such stacks can be several feet high, and with the weight of multiple layered corrugated composition, the stacks can weigh a thousand pounds or more.
Further, for some applications, it is desirable that the blanks or sheets be inverted prior to feeding same to some unit operations in the paperboard products plant. An example is where sheets, having been printed on one side, require inverting prior to being passed to another printing operation. Accordingly, one of the work functions addressed herein is that of providing an inline inverter assembly for inverting blocks of the sheets prior to the shingling operation.
One difficulty with prior art prefeeders of the type under consideration herein is that such prior art prefeeders have required considerable height in order to accommodate very tall stacks of paperboard container blanks. It would be very useful if the work functions addressed by the present invention could be carried out with machinery that is readily accessible by operating personnel substantially at floor level.
None of the prior art prefeeders known to the present inventors achieves these desired improvements. It is to that end to which the present invention is directed.